1. Field of the Invention
The invention herein described relates to a marker system for use with a medical navigation system, wherein the marker system includes interchangeable tracking marker holders and bases for attaching the marker holders to instruments that are to be tracked during a medical procedure.
2. Description of the Prior Art
Medical navigation systems, such as image-guided surgery systems, provide medical practitioners, such as surgeons, with navigation information by registering pre-operative images to the physical space of a patient. Most existing systems provide instrument guidance, indicating the position of the instrument in the pre-operative images on a display during the medical procedure. Navigation guidance systems provide increased confidence and precision in the use of medical instruments.
Navigation guidance systems use a computer to which one or more tracking sensors are connected. The tracking sensors track the position of artificial or natural landmarks (herein generically referred to as tracking markers) affixed to the patient and/or instruments, whereby the position of the patient and/or instruments can be determined and registered to pre-operative images of the patient. These tracking markers include active emitters that emit electromagnetic, magnetic or acoustic signals to one or more tracking cameras or devices, and passive reflective markers that reflect light to one or more tracking cameras. The medical instruments with which such tracking markers have been employed include pointers, scalpels, forceps, microscopes, ultrasonic transducers, etc.
Heretofore, adapters have been used to attach replaceable passive reflective markers to surgical instruments. This allowed surgeons to use surgical instruments with which they were more familiar than the specially manufactured surgical instruments that used active tracking markers. The passive reflective markers could be removed for sterilization of the surgical instrument in an autoclave and new reflective markers installed for the next surgical procedure.
The present day adapter typically includes an adapter body including a fastener base and three or more arms that radiate outwardly from the fastener base. The distal ends of the arms have mounts to which respective reflective markers are removably attached. The fastener base includes a clamp for attaching the adapter body to the medical instrument or body part to be tracked by the navigation system. In order to track multiple instruments, adapters having different characteristic arrangements of the reflective markers are provided. Different characteristic arrangements are obtained by varying the length and angular relationships of the adapter arms. Because of the central mounting (or hub) portion and the radiating arms with the reflective markers at the distal ends thereof, the adapters with the reflective markers are often referred to as reference stars.
A well-known navigation system that uses the aforedescribed reference stars is the VectorVision™ image-guided navigation system, available from BrainLAB AG.